A preliminary study was conducted in the absence of nitrogen fertilizer to determine the effect of field use conversion on soil nitrogen uptake by pakchoi. Some of the mineral nitrogen retained by biochar was still bioavailable for uptake by plants in the soil.
Data on biochar addition are not well documented when it comes to vegetable production systems (Jia et al., 2012). Effects of biochar addition on vegetable (pakchoi) nitrogen uptake and recovery efficiency in vegetable production systems.
Introduction
National food security is a serious issue in China due to its large population and limited area per capita of cultivated land (Chen, 2007; Chen et al., 2013). Excessive nitrogen fertilizer application is common in the vegetable production system, along with low nitrogen uptake efficiency (Huang et al., 2006; . Ju et al., 2011; Zhu et al., 2005).
Conversion of field utilization patterns in China
- Food demand increases pressure on cultivated land
- Conventional crops field converts to vegetable field
A review of international literature shows that a decrease in cultivated land area occurs not only in China, but also in other developing countries (Ramankutty et al., 2002). There was 0.2 million hectares of cultivated land converted to non-agricultural use annually during the period and more than 1.5 million hectares annually after 2000 (Deng et al., 2006).
Nitrogen processes in the vegetable production system
- Comparison of nitrogen input in a vegetable production system to that in a
- Comparison of nitrogen output in vegetable production systems with that in
As a result, nitrogen mineralization processes in a vegetable production system must meet plant nitrogen demand (Li et al., 2003). The amount of nitrogen fertilizers applied is usually much higher than the amount recommended in vegetable production systems (Zhu et al., 2006).
Lack of concern for nitrogen processes in vegetable production systems
On the other hand, vegetable production is expanding rapidly, leading to the appearance of large agribusiness companies. Large fields are rented for 3-5 years for vegetable production with the aim of making a profit as soon as possible, without paying attention to soil health because they will leave and find another field when the soil condition is no longer suitable for planting .
Biochar addition changes nitrogen processes in cultivated system
- Effects of biochar addition on soil nitrogen content and transformations
- Effects of biochar addition on plant growth
- Effects of biochar addition on nitrogen loss
Increasing the retention of water can also reduce nutrient movement and leaching (Major et al., 2010). Furthermore, the adsorption of biochar will lower the ammonium nitrogen content in soil (mentioned in 1.3.1.1) (Ding et al., 2010;.
Biochar in China: Status quo of research and trend of development
- Raw material
- How to use
- Biochar production patterns in China
For example, straw production in China accounts for 20%-30% of global straw production (Wang et al., 2010). Countries with intensive production and countries with low fertility should be prioritized for biochar addition (Chen et al., 2013).
Conclusion
The effect of biochar addition on N 2 O and CO 2 emissions from a sandy loam soil – the role of soil aeration. Effect of biochar amendment on yield and methane and nitrous oxide emissions from a rice field from Tai Lake plain, China.
Introduction
Plant nitrogen uptake and nitrogen loss are the main methods of nitrogen output (Wen et al., 2017). Several studies in the literature have reported that soil nitrogen losses through leaching contribute to more than half of nitrogen loss in cropland (Min et al., 2011a).
Sampling site background information
The change in land use from growing conventional crops such as corn, wheat, and rice to vegetable production is also occurring in northern China, where farmers are planting vegetables in the fields previously used for planting corn and wheat. The effects on soil nitrogen processes are likely to be significant when fields previously used for paddy production are converted to vegetable fields in the Tailake region instead of maize/wheat field conversion to vegetable production in northern China.
MATERIALS AND METHODS
- Experimental site selection and description
- Soil sampling
- Pot experiment and plant sampling
- Simulation of leaching and leachate sampling
Each soil sample (20 kg) was collected from the top 0-20 cm through a combination of 10 pores for each field. Leachate from the six soils was collected via a tray placed under each pot, which collected the liquid flowing from the three pores at the base of the pot.
Sample analysis
- Soil
- Plant
- Leaching
- Nitrogen output
- Statistical analyses
Available soil K: An air-dried soil sample was extracted with 1 M ammonium acetate (soil:solution ratio was 1:10) for 1 h and the K concentration of the extract was determined by flame photometry. Total soil nitrogen content (Total N): An air-dried soil sample was used to determine total N using the Kjeldahl method.
Results
- Chemical properties of soils
- Yield and nitrogen uptake by the vegetable plant
- Nitrogen leaching loss
SDs in the same color with the same letters are not significantly different, determined by Duncan's multiple range test (P<0.05). a) Nitrogen uptake by pakchoi in pair 1 (b) Nitrogen uptake by pakchoi in pair 2. In the other growing seasons, the difference of nitrogen uptake by pakchoi between vegetable and spruce soils was not significant (P>0.05).
Discussion
- Changes in soil pH values, organic matter and mineral nitrogen contents
- Soil nitrogen output from the two fields
The increased content of mineral nitrogen in the crop soils can be attributed to high amounts of nitrogen fertilizer application before sampling from the vegetable fields. The timing of collection was a possible explanation for the lower mineral nitrogen content of the topsoils.
Conclusion
Evolution of soil chemical properties over the past 50 years in the Tai Lake region of China. Soil and crop management practices for increased productivity of a rice-wheat cropping system in Sichuan Province, China (Eds Hobbs PR and Gupta RKO: 1-10.
Introduction
Vegetable production often requires a higher supply of nitrogen and irrigation water (Shi et al., 2009; Qiu et al., 2010). Nitrogen is mainly lost through leaching in the form of nitrate nitrogen (Min et al., 2011).
Materials and methods
- Soil description
- Planting material
- Biochar characterization
- Pot experiment
- Simulation of leaching
- Sampling
Therefore, it is imperative to study the effect of adding biochar to soils used for vegetable production in intensive cropping systems and to determine the effect on nitrogen retention (including soil mineral nitrogen content, bioavailability of mineral nitrogen retained by biochar and resulting nitrogen losses as a result of leaching ) in vegetable fields. The objectives of this study were to (1) investigate the effect of biochar on soil mineral nitrogen retention, (2) determine the bioavailability of mineral nitrogen retained by biochar, (3) investigate the effect of biochar addition on leaching nitrogen loss.
Sample analysis
- Soil and biochar
- Leachate
- Statistical analyses
PM(BC to soil)= w(MN on BC)/w(MN in S) (Equation 3.6) Where, PM(BC to soil) = the percentages of mineral nitrogen of biochar, w(MN in S) = the mineral nitrogen content in soil. Nitrogen mineralization rates were calculated as the difference between final and initial soil mineral nitrogen content divided by 35 days (Stanford and Smith, 1972).
Results
- Mineral nitrogen contents in soils
- Mineral nitrogen retained by biochar
- Nitrogen mineralization and nitrification rates in soils
- Nitrogen leaching loss
The use of nitrogen fertilizers increased both the content of ammonium nitrogen and nitrate nitrogen in the soil (Figure 3.3 b, Figure 3.3 d). Similar to the trend under nitrogen-free conditions, biochar addition significantly increased soil ammonium nitrogen content under nitrogen conditions.
Discussion
- Biochar nitrogen retention
- Effect of biochar addition on nitrogen mineralization and nitrification
- Effect of biochar addition on nitrogen leaching loss
- Biochar additional rates
The negative effect of biochar addition on nitrogen mineralization was observed in the 1st season (only significant in the no-nitrogen condition). Furthermore, the effect of biochar on the soil nitrification rate was only observed in the nitrogen state (Fig. 3.5).
Conclusion
Impact of biochar addition on water retention, nitrification and carbon dioxide evolution from two sandy loam soils. Effect of biochar amendment on sorption and leaching of nitrate, ammonium and phosphate in a sandy soil.
Introduction
The acidifying effect of enhanced nitrification due to biochar addition can counteract the calcification effect of biochar (Zhao et al., 2014). This implies that the effect of biochar on soil pH values may change as the growing season continues.
Material and Methods
- Soil and biochar description and characterization
- Experimental design
- Soil sampling
Other nitrogen processes affected by the addition of biochar can also have an effect on soil pH levels. The change in soil pH due to biochar addition may be much smaller than predicted.
Sample analysis
- Soil pH value, soil organic matter content and base contents
- Soil pH buffering capacity
- Acidification rate
- Statistical analyses
K+ and Na+ contents were determined by flame photometry (Sherwood Corp., UK) and Ca2+ and Mg2+ contents by atomic absorption spectrometry (Shimadzu Corp., Japan). The analysis of the correlation relationships between indices indicating soil acidity and the content of organic matter, bases and aluminum was performed by means of bivariate correlation analysis with significance levels of 5% or 1% (SPSS ver. 16.0 for Windows, SPSS Inc ., USA).
Results
- Soil pH among different treatments
- Soil pH buffering capacity and acidification rates
- Soil organic matter content and major base content
- Relationships among soil pH value, pH buffering capacity, acidification rate
Compared to the soil pH value before this experiment (Table 4.1), treatments in nitrogen-free fertilizer increased pH values (ΔpH was positive in the table) while treatments in nitrogen-free pH decreased (ΔpH was negative in the table) after four increments. season. Biochar addition increased soil pH buffering capacity by 16%–32% and 13%–27% under nitrogen-free and nitrogen-free conditions, respectively.
Discussion
- Factors affecting soil acidity by biochar
- Effect of biochar addition on soil pH values in two nitrogen conditions
- Effect of biochar addition on soil pH buffering capacity and acidification rate
- How to evaluate the effect of biochar on soil acidity?
Biochar addition effectively reduced soil acidity under nitrogen-free conditions and maintained soil pH values under nitrogen conditions (Figure 4.1 and 4.2). Soil pH values may not reflect changes in soil acidity caused by soil processes (Fidel, 2012).
Conclusion
Instead, many soil processes influenced soil acidity in this study, as discussed above. The buffering capacity of soil pH should be selected as an auxiliary indicator for evaluating the effect of biofuel on soil acidity (Eckert and Sims, 1995).
Introduction
On the other hand, high nitrogen loss due to leaching and large amounts of nitrogen remaining in the soil can limit NRE in vegetable production systems (Ding et al., 2010). It has also been shown that the addition of biochar can effectively reduce N2O emissions in vegetable production systems (Jia et al., 2012).
Material and Methods
- Soil and biochar description and characterization
- Planting material
- Use of 15 N tracing in comparing nitrogen sources
- Crop harvesting and biochar sampling
Few studies have examined plant nitrogen uptake, nitrogen left in the soil and nitrogen loss. Stable isotope 15N-traced fertilizers were used to (1) determine the effect of biochar on plant nitrogen uptake and plant yield, (2) investigate the recovery of nitrogen fertilization in plants, soil and leachate at different biochar addition rates and (3) determine. the sources of nitrogen (fertilization and soil mineralization) related to plant nitrogen uptake, nitrogen remaining in the soil and nitrogen loss.
Analysis
- Plant tissue analysis
- Soil and biochar analysis
- Leachate analysis
- Calculations
- Statistical analyses
The other parameters (Pf, Ps, Nf, Ns and NR) were all calculated with the values of N and A. The percentages of nitrogen from manure and soil were calculated with equation 5.4 and 5.5 (Zhang et al., 2012).
Results
- Yields of pakchoi
- Nitrogen uptake by pakchoi and NUE
- Nitrogen uptake by Pakchoi plants from two nitrogen sources (labeled fertilizer
- Recovery of fertilizer nitrogen ( 15 N)
- Nitrogen outputs and their sources
Treatments with biochar addition (U1%BC and U5%BC) showed a higher amount and percentage of nitrogen fertilizer reduction in the 4th season. In the no-nitrogen condition, nitrogen uptake by pakchoi plants and in the leachate was all from soil mineralized nitrogen.
Discussion
Nitrogen in the fertilizer left in the soil was shown to have no effect on nitrogen uptake by plants in this study. A decrease in NRE in pakchoi was found in season 2, corresponding to a large increase in nitrogen loss (Table 5.3).
Conclusion
Effects of a catch crop and reduced nitrogen fertilization on nitrogen leaching in greenhouse vegetable production systems. Nitrogen fertilizer use in China – Contributions to food production, environmental impacts and best management strategies.
- Introduction
- Responses of major findings to the objectives of this study
- Differences in nitrogen processes and soil chemical properties between paddy
- Effect of biochar addition on soil nitrogen retention in vegetable soil
- Effect of biochar addition on vegetable soil acidity
- Effect of biochar addition on plant nitrogen uptake and yield
- Amount of nitrogen from two sources and nitrogen recovery efficiency of plant
- General conclusion
- Advices for future work
- How to determine whether the soil should be added biochar?
- How to determine the optimal biochar addition rate and frequency?
- Use biochar as a carrier for nitrogen transport
To determine the effect of biochar addition on soil acidity in soils used for vegetable production in China. To determine the effect of biochar addition on nitrogen uptake by vegetables (pakchoi) and yields.
